Every day nearly a million commuters travel on the Northeast Corridor -- the vast rail network between Washington, D.C. and Boston.

Many of those passengers cross over a small river in the coastal city of Norwalk, Connecticut. But the only way for a train to get across that river is on the Walk Bridge -- a 120-year-old “swing bridge.”

Sometimes, when the Walk Bridge swings open to let boats pass through, it gets stuck, causing chaos for train commuters. State officials want to replace it.

The Norwalk River Railroad Bridge is known locally as the Walk Bridge. It has two jobs: carry hundreds of trains over the river every day, and swing open for boat traffic between Long Island Sound and the Norwalk River.

“Although we call it a bridge, you have to keep in mind that it’s much more than a bridge. It’s actually a machine as well as a bridge,” said Bruce Clouette, a historian who’s studied moveable bridges in Connecticut.

"There are tons of moving parts, there are control systems, and there is a drive mechanism,” Clouette said. “That really makes this different from just a simple bridge that goes from point A to point B and happens to cross a river.”

The huge steel structure rotates on a circular pier, opening a channel on the river that larger boats can pass through. It takes a crew of eight about 10 minutes to open and close the bridge.

Watch the Walk Bridge in action below:

The Walk Bridge was built in 1896 -- and for the most part, it’s stood the test of time, swinging open for boat traffic a few hundred times a year.

But in 2014, the bridge got stuck open -- twice. Hundreds of train commuters were stranded.

The Walk Bridge had malfunctioned before, but officials said this was the first time they had significant concerns with the bridge’s functionality. It got stuck again in 2016.

Jeff Portal is an engineer with the Connecticut Department of Transportation.

“Like the human body, no matter how much medicine you put into it, eventually something is going to give out,” Portal said.

Jeff Portal, an engineer for the Connecticut Department of Transportation, stands in front of the Walk Bridge in March 2017.

Credit Ryan Caron King / NENC

And now, the bridge is nearing the end of its useful life. DOT Commissioner Jim Redeker said it’s a single point of failure for the entire region -- and needs to be replaced.

“The current Walk Bridge -- 120 years old -- is a single structure with four tracks on it,” Redeker said. “So when it fails, the entire Northeast Corridor and New Haven Line cannot operate.”

The bridge also has a large presence in the city of Norwalk. The bridge’s steel beams sit only a few feet away from an aquarium at the center of the commercial district.

Debora Goldstein is the commissioner of a local electric utility. She thinks the state should rehabilitate the current bridge instead of building a new one.

Debora Goldstein is the commissioner of a local electric utility.

Credit Ryan Caron King / NENC

“The question of whether Norwalk should suffer the pain on behalf of this complete reconstruction is partly weighed against the need of the commuters of the entire Northeast Corridor who need to get reliably through from here to there,” Goldstein said.

The federal government is also planning to run new high speed trains through the region over the next few decades. Goldstein said she thinks it’s better to wait for those plans to sort out before making big investments -- especially investments that could have such a big impact on the small city.